Known to the electrostatographic fixing art are various fuser members adapted to apply heat and pressure to a heat-softenable electrostatographic toner on a receiver, such as paper, to permanently fuse the toner to the receiver. Examples of fuser members include fuser rollers, pressure rollers, fuser plates and fuser belts for use in fuser systems such as fuser roller systems, fuser plate systems and fuser belt systems. The term “fuser member” is used herein to identify one of the elements of a fusing system. Commonly, the fuser member is a fuser roller or pressure roller and the discussion herein may refer to a fuser roller or pressure roller, however, the invention is not limited to any particular configuration of fuser member.
One of the long-standing problems with electrostatographic fixing systems is the adhesion of the heat-softened toner particles to the surface of a fuser member and not to the receiver, known as offset, which occurs when the toner-bearing receiver is passed through a fuser system. There have been several approaches to decrease the amount of toner offset onto fuser members. One approach has been to make the toner-contacting surface of a fuser member, for example, a fuser roller and/or pressure roller of a non-adhesive (non-stick) material.
One known non-adhesive coating for fuser members comprises fluoropolymer resins, but fluoropolymer resins are non-compliant. It is desirable to have compliant fuser members to increase the contact area between a fuser member and the toner-bearing receiver. However, fuser members with a single compliant rubber layer absorb release oils and degrade in a short time leading to wrinkling artifacts, non-uniform nip width and toner offset. To make fluoropolymer resin coated fuser members with a compliant layer, U.S. Pat. Nos. 3,435,500 and 4,789,565 disclose a fluoropolymer resin layer sintered to a silicone rubber layer, which is adhered to a metal core. In U.S. Pat. No. 4,789,565, an aqueous solution of fluoropolymer resin powder is sintered to the silicone rubber layer. In U.S. Pat. No. 3,435,500, a fluoropolymer resin sleeve is sintered to the silicone rubber layer. Sintering of the fluoropolymer resin layer is usually accomplished by heating the coated fuser members to temperatures of approximately 500° C. Such high temperatures can have a detrimental effect on the silicone rubber layer causing the silicone rubber to smoke or depolymerize, which decreases the durability of the silicone rubbers and the adhesion strength between the silicone rubber layer and the fluoropolymer resin layer. Attempts to avoid the detrimental effect the high sintering temperatures have on the silicone rubber layer have been made by using dielectric heating of the fluoropolymer resin layer, for example see U.S. Pat. Nos. 5,011,401 and 5,153,660. Dielectric heating is, however, complicated and expensive and the fluoropolymer resin layer may still delaminate from the silicone rubber layer when the fuser members are used in high-pressure fuser systems. U.S. Pat. Nos. 5,547,759 and 5,709,949 to Chen, et al. disclose a method of bonding a fluoropolymer resin to various substrate including silicone via a layer of fluoroelastomer layer and fluoropolymer containing polyamide-imide layer. But this requires a thin base layer to prevent the degradation of silicone base cushion substrate during the sintering process. U.S. Pat. Nos. 5,998,034 and 6,596,357 to Marvil et al. also discloses a multilayer fuser roller having fluopolymer coating on a compliant base layer. However, this requires pre-baking steps in an infrared oven to prevent the degradation of primer layer and silicone base cushion. In addition, a fuser member made with a fluoropolymer resin sleeve layer possesses poor abrasion resistance and poor heat resistance.
U.S. Pat. No. 7,195,853 describes a process for fusing toner employing a fuser roller having a surface layer that includes both a fluoroelastomer continuous phase, and also a discontinuous phase dispersed through the continuous phase in the form of domains. A problem with such fuser members, however, is that both the fluoroelastomer continuous phase and the discontinuous phase dispersed through the continuous phase are in the form of domains consisting of silicones, fluorosilicones, fluoroelastomer and perfluoropolyethers, which are high surface energy materials which can not release toner under oil-less fusing conditions.
U.S. Pat. Nos. 7,494,706; 7,531,237; 7,534,492; and U.S. Publication No. 2007/0296122 describe fuser members and methods of making such fuser members wherein the outer layer of the fuser member comprises an annealable fluoropolymer resin. While fluoropolymer resins typically provide an excellent non-stick material, it provides little compliance and conformability. While use of a cushion layer between the fuser member substrate and the outer layer improves performance, the non-compliant outer layer itself still encounters problems when fusing toner to various types of printed substrates. Fuser roller coating materials comprising polyperfluoroalkoxy-tetrafluoroethylene (PFA) dispersion coating as a roller top coat typically have three major issues: 1) high print gloss especially for uncoated heavy weight paper; 2) the fuser surface has surface cracking, in-track/x-track cutting under high stress and high loaded condition; and 3) insufficient contact of the PFA fuser surface to the rough toner image area for texture paper due to the non-compliant PFA surface. Additionally, outer layers comprising fluoropolymer resins typically require relatively high temperatures during manufacture thereof in order to sinter particulates of such fluoropolymer resin to form an integral layer coating, which high temperatures may be detrimental to underlying cushion and adhesive layers comprising relatively temperature sensitive materials.
For the foregoing reasons, there is a need for fuser members and a method of fabricating fuser members which have a fluoropolymer resin layer, and optionally a thick compliant layer or layers, to solve all the three major problems of the conventional PFA coatings without compromising the unique characteristics of PFA coating such as low surface energy, low C.O.F., tough mechanical property, high temperature resistance and annealing surface, and which does not subject the fuser member to high temperatures typically required for sintering of fluoropolymer resin particulates.